Monthly Archives: May 2014

I was looking at some corn Monday and it is progressing well. Most is waste high or as tall as me, up to vegetative growth stage – V10. One thing we are watching for is disease. There is no known southern rust yet. However, Northern corn leaf blight and Northern corn leaf spot are two diseases being reported. Seminole Ag Agent, Rome Ethredge has seen both of these diseases and has some pictures. Here is a photo of Northern corn leaf blight:

NCLB is more likely to be found in corn behind corn and with susceptible varieties. Its presence in the field does not automatically warrant a spray. Here are some thoughts from UGA Extension Pathologist, Dr. Bob Kemerait:

All growers should scout for NCLB.

All growers should recognize that conditions are generally favorable for NCLB.

If after scouting, no lesions, or only a very few are found, delay applying fungicides.

If more lesions are found or a susceptible hybrid is planted, grower should way options for protecting crop BEFORE tassel.

Another disease that showed up last year was Northern corn leaf spot. The spots look similar but has this barky, tree bark appearance. Here is a photo by Seminole Ag Agent, Rome Ethredge:

Northern corn leaf spot is DIFFERENT than Northern corn leaf blight. Here are some comments from Dr. Kemerait:

I do not have any data on the use of (or need for) fungicides in the management of northern corn leaf spot. In discussions with Dr. Dewey Lee, we are both uncomfortable with reports of this disease this early. Although I do not have recommendations for use of fungicides on this disease, growers need to be aware that it is active in the state. Also, I believe that growers should assess the development of this disease and may consider us of fungicides IF development and spread seems to occur in the field. Again, at this time, we do not have recommendations for Northern corn leaf spot.

Wheat is moving into the soft dough stage and starting to turn brown. Once the water content of the kernels drops to around 30%, the plant loses most of the green color but the kernels can still be cut by pressing with a thumbnail. This is at hard dough stage and marks the end of all insect and disease management.

In terms of Fusarium head blight, according to Extension Pathologist, Dr. Alfredo Martinez, the damage was done during flowering and fungicide sprays after the fact will not help. I am still seeing it in fields. There is nothing we can do now except harvest early, turn up the air during harvest and separate bad fields.

UGA Extension Grain Agronomist, Dr. Dewey Lee, says this concerning Fusarium head blight. “I believe yield loss will be severe in some fields depending on many things. The infection process of FHB begins when the anthers extrude beyond the glumes and are infected by Fusarium. It requires the type of weather we had this year, lots of rain, wet conditions during flowering with moderate temperatures. Infected flowers either abort or develop kernels that are typically shriveled and may demonstrate a pink discoloration (from the mycelium). The pathogen will produce a mycotoxin, DON (deoxynivalenol). This fumonisin is often rejected in the market at level above 2 ppm. Because of this, I encourage growers to blow as much air as possible to take out the lower test weight/shriveled grain.

My suggestions is to harvest as early as possible and make sure to separate bad fields from your good fields.”

Cotton is coming up now and we are seeing first true leaves. I did a count for thrips yesterday and found them to be over threshold. This is an area in the county which is notorious for having high thrips populations. I was finding both mature and immature thrips which warrant a spray, and also thrip numbers of 3-4 per plant also warrants a spray.

We were also noting some herbicide damage with rain at germination. One thing we are finding is cotyledons cupping. Cupping of the leaves is evident of thrips damage – we are seeing this with true leaves and cotyledons. However, UGA Extension Entomologist, Dr. Phillip Roberts, says cupping on the cotyledons is NOT from thrips injury. The only thrips injury we would observe on cotyledons is silvering on the underside of cotyledons where the thrips were feeding, not mishapen cotyledons. That would differentiate some herbicide injury. Nonetheless, a thrip spray would lessen some stress on the plant.

Corn is still looking rough in some fields. Michael Murray and I looked at some corn end of last week that was showing nutrient deficiencies. Corn appeared to have signs of nitrogen, sulfur, magnesium and potash deficiency, but tissue analysis show they were sufficient. Another thought was since Counter was used at planting, could it cause problems. You can have issues there if ALS herbicide were used along with Counter, but in this case, ALS were not used.

So far, a nematode analysis has been taken, and we cannot rule this out since reports of stubby root nematode have been common this season. The N:S ratio was 32:1 which should be less that 16:1. In either case, additional S is needed. Mg and K should be checked again in two weeks to be sure that the plants are continuing to take up enough. Some 28-0-0-5 would help to get back some N and S.

It seems like everyone is scrambling to get caught up since rain has let off. Timing on cotton and peanut planting is not far off, but it could push back planting of other crops and force us to prioritize. I was asked about soybeans and effects of late planting. In this situation, we may need to prioritize. They were going to plant a maturity group 5, 6 and 7. These two slides from UGA Extension Soybean Agronomist, Dr. Jared Whitaker, show the effect of planting date on soybean yield:

The first slide shows overall yield affected by planting date. Bottom line is that the later you plant the lower the yield potential.

The second slide shows data demonstrating the effect maturity group has on planting date. Bottom line here is that the earlier maturing varieties lose yield potential much faster as planting date gets later compared to later maturing varieties.

We’re starting to get caught up from a week of planting trials last week. Grady County Ag Agent, Brian Hayes, was with me when we stopped by Ronnie Herring’s house to look at some damage to his young Elliot pecans. The leaf tips appeared to be scorched and looking closer Brian found a little worm boring into the stem (below).

The pecan budmoth (Gretchina bolliana) is a native pest of pecan and incurs most damage on young, transplanted trees. They overwinter as adults under bark scales then lay eggs on twigs, buds, and shoots in the spring. Once eggs hatch, the larvae feed on and in new buds, shoot apices, and leaves.

The larvae are creamy to dirty white at first, but mature budmoth larvae are one-half inch long, yellow-green, with dark brown head capsules. Once they finish feeding, the larvae pupate in rolled up leaves and damaged buds. It takes about a month for pecan budmoths to complete a generation.

Treatment of mature trees for budmoth is usually not needed or is accomplished through normal spraying of other pests. Control in nursery stock or for newly transplanted trees includes monitoring for budmoth infestation and treated according to need.

Pecan growers need to be irrigating after a week of no rain. Here are some irrigation recommendations from UGA Extension Horticulturalist, Dr. Lenny Wells:

Pecan trees need as much as 350 gal/tree/day as they are filling the kernels in August and September. While they need good soil moisture throughout the growing season, the demand for water is much less early in the season than later. As the nuts begin to size, the demand for water increases, so growers need to begin applying water at low rates early in the season and increase as the crop develops.

We are fortunate in the Southeastern U.S.that we normally get enough rainfall throughout the year to account for at least 30-50% of the tree’s water needs. The problem is that the distribution of that rainfall is not always timely to the tree’s needs. The table above summarizes our irrigation schedule recommendations for bearing pecan trees in Georgia. Take note that the irrigation can be turned off for 3 days following rainfall events of 1″ or more per day. Orchards on sandy soils should lean toward the high end of the recommended range, while clay soils can lean to the low end.

We know that young, non-bearing trees (<5 yrs old) do not require near the amount of water applied to mature trees in late season. While we don’t have firm, research-driven numbers to provide for irrigating young trees at this point, we are currently in the process of developing these. In the meantime, the April or May rates applied to mature trees will work season long for young trees because there is no crop demand on them.